Color stabilization of light distillates



Patented Apr. 6, 1943 COLOR STABILIZATION OF LIGHT DISTILLATES Amiot P.Hewlett, Summit, N. J., assignor to Standard Oil Development Company, acorporation of Delaware,

No Drawing. Application August 10, 1940,

Serial No. 352,132

7 Claims.

This invention relates to stabilization of light petroleum .distillates,such as refined gasoline,

It is known to those skilled in the art that even highly refined lightdistillates which are substantially colorless or water white generallycontain components that under the accelerating photo-chemical action ofsunlight cause discoloration. The undesirable changes in the appearanceof the product made by this discoloration while the product is beingstored or marketed makes the product unattractive, of lower value, andunsalable. Although dyes may be used in some of the products, such asgasoline, to mask the defect of color instability, they do not reallycorrect this defect permanently, because the hydrocarbon productinherently continues to undergo changes in color, with the result thatthe dyed product will change in appearance.

An object of this invention is to provide a method for stabilizing thecolor of refined petroleum products by an agent which functions veryefiectively for this purpose when added in small inexpensiveconcentrations and which has no deleterious effects in the uses of theproducts.

A further object is to provide purified low boiling petroleumdistillates of light color with high color stability and of such purityand proper composition to meet commercial requirements.

This invention is based on the discovery that certain dihydric alcoholshaving suitable miscibility with petroleum products, more particu-,

larly the alkanediols or alkylene glycols containing 4 or more carbonatoms, such as pentanediols, when present in the light colored petroleumproducts in very small concentrations, of less than 1% or of the orderof 0.05% to 0.2% by weight, function very satisfactorily in decreasingthe tendency of these products to lose color even when these productsare subjected to highly intensified sunlight stability tests.

It was found that this type of stabilizing agent should be preferably adihydroxy alcohol saturated with respect to carbon bonds and should havea sufficiently low melting point in order to be suitably soluble in thehydrocarbon distillate, for otherwise it has a tendency to be thrown outof solution and thereby make the product cloudy.

The more specific varieties of these alcohols which may be selected is amatter of economy andspecific use of the product in general, thedihydric alcohols having from 4 to 5 carbon atoms per molecule areconsidered the most useful under'ordinary conditions, but dihydricalcohols having up to '8 carbon atoms per molecule may also be employed.

The literature describes a number of methods by which compounds of thisclass can be prepared. One of the general methods involves halogenationof a suitable hydrocarbon followed by hydrolysis of the dihalide. Thereare a number of commercial processes which make available some of thepreferred dihydric alcohols, as for example the pentanediols which areprepared by catalytic hydrogenation of furfuryl alcohol or acetylacetone. While such commercial procedures tend to form isomeric mixturesof the dihydric alcohols, it is found that they make available thedihydric alcohols which are of particular interest, namely, those inwhich the hydroxyl group are attached to non-adjacent carbon atoms, i.e. the carbons of the hydroxyl group are in the beta gamma, or deltapositions, as for example mixtures of pentanediols comprisingprincipally pentanediol-1,5 and -2,4.

The following example is presented to illustrate the use of the dihydricalcohols as color stabilizers 'and to demonstrate their effectiveness:

Example A sample of refined gasoline having a +24 Saybolt color was usedas a base stock. Pentanediols obtained as a by-product from the manufacture of tetrahydrofurfuryl alcohol was added to this base stock in aconcentration of 0.1% by weight. Samples of this blend and of the basestock run as a blank were exposed to direct intensified light having thewave length characteristic of mid-day summer sunlight for periods of 15,30, 60, and minutes in Pyrex glass bottles. The following data wereobtained:

Color, Saybolt Sampln After exposure to the light for Origs 2.0 so 180mm. mm. mm. min.

1. Gasoline base +24 +13 1 +3 +0 2. Gasoline base +01% pentanediols..+23 +17 +13 +12 +9 It is to be observed that the color stabilizingaction represented by that of the added dihydric alcohol is a ,verysignificant improvement, for it means that such compositions would notnoticeably discolor to the naked eye when exposed to diflused sunlightin ordinary glass containers over very long periods of time.

The color stabilizing agents of this invention are of great value forstabilizing solvents and krrosene, which in general are desirably usedin water white condition. In gasoline the stabilizing agents may be usedtogether with dyes and other types of agents used to increase theantiknock value or to improve the fuel in other respects. They may beadded to the hydrocarbon products derived from petroleum by straightdistillation or by any of the known conversion I processes, and afterthese products are given the customary refining treatments with acids,bases, salts, clays and the like; also, they may be added prior to afinal filtration treatment.

It is to be understood that this invention is subject to variousmodifications, as for example, the dihydric alcohols may contain abranched alkyl group or some substituent group such as an amino group,and is not to be limited by the specific example given for the purposeof illustration.

I claim:

1. The method of stabilizing the color of a refined substantiallycolorless light petroleum oil product which comprises dissolving in saidproduct a small but sufficient proportion of pentane diol in the rangefrom 0.05% to about 1% by weight to suppress discoloration of theproduct by the action of sunlight radiations.

2. The method as described in claim 1 in which radiations.

said pentanediol contains hydroxyl groups attached to non-adjacentcarbon atoms.

3. A refined substantially colorless petroleum distillate oil blendedhomogeneously with a suificient proportion of pentanediol ranging from0.05% to about 1% by weight'tor suppressing discoloration of the oil bythe action of sunlight 4. A composition as described in claim 3 in whichsaid pentanediol consists of the isomers pentanediol-1,5 andpentanediol-2,4.

5. A motor fuel blend comprising substantially colorless refinedgasoline hydrocarbons blended with a suflicient proportion ofpentanediol ranging from 0.05% to about 1% by weight or saidhydrocarbons to suppress discoloration of the blend by the action ofsunlight radiations.

6. A substantially colorless refined kerosene blended homogeneously witha sufficient proportion of pentanediol ranging from about 0.05% to about1% by weight to suppress discoloration of the kerosene by the action ofsunlight radiations.

'7. A color stable solvent comprising a refined naphtha solvent blendedhomogeneously with a suflicient proportion of pentanediol in the rangefrom 0.05% to about 1% by weight to suppress discoloration oi thenaphtha solvent by the action of sunlight radiations.

AMIOT P. HEWLET

